Correlation of Cryogenian diamictites between Svalbard, East Greenland and northern Fennoscandia.

The global synchroneity of Neoproterozoic diamictites is key to “Snowball Earth” hypothesis, yet correlations between disparate occurrences is often challenging. The most commonly used method from correlating Neoproterozoic deposits is through the magnitude and presence of carbon isotopic anomalies associated with global climatic excursions. Sediment composition, and in particular its provenance can be used to test palaegeographical and palaeoenvironmental models and provide additional constraints on correlation. In addition, provenance can shed light on genesis such as providing evidence for exotic or far-travelled material consistent with a glacigenic origin.

The Polarisbreen Group is a Cryogenian diamictite bearing succession, which forms part of the Eastern Terrane in Svalbard. Its palaeogeography is poorly constrained and it may have originally formed part of Laurenetia, or may have been an independent microcontinent. In this study, the palaeogeographic position of the Cryogenian succession of eastern Svalbard is evaluated by multi proxy provenance analysis including QEMSCAN, Pb isotopic composition of detrital K feldspar and field-based clast counting. The results are compared with data from the Tillite Group Formation of East Greenland, which is thought to have been deposited in close proximity, with the Eastern Terrane formerly adjacent East Greenland in the vicinity of Ella Ø, Kong Oscar Fjord. These signals are also compared with those obtained from the Smalfjord and Mortensnes formations in northern Fennoscandia. This was done to evaluate the value of the provenance tools as the Fennoscanidan and East Greenland successions were sourced from different continental landmasses.

Pb isotopic patterns from the East Greenland and Svalbard units are strongly overlapping, consistent with a similar provenance and thus their correlation and depositional proximity. Perhaps one of the more striking elements comes from the Fennoscandian successions. The Pb isotopic data from autochthonous Smalfjord and Mortensnes units differ subtly, both have patterns overlapping with Pb isotopic signatures from Fennoscandia. However, the pattern from the Smalfjord Formation within an allocthonous Caledonian nappe is highly exotic for the region. The value of the Pb isotopic data for correlation is of these units within Fennoscandia is underscored, whereby one diamictite assigned to the Smalfjord Formation has a Pb isotopic pattern that is compatible with neither of the autochthonous Mortensnes or Smalfjord diamictites. The provenance data and field observations suggest the stratigraphy in this region may be erroneously correlated.